Boxer knocking the stuffing out of Teddy boy (5)
I believe the answer is:
tyson
'boxer' is the definition.
(US boxer Mike Tyson)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for tyson that I've seen before include "Mike ..., former US prizefighter" , "Mike --, US boxer" , "26 4 [RING MASTER]" , "Youngest ever undisputed world heavyweight boxing champion, b, 1966" , "Undisputed world heavyweight champion, 1987" .)